Abstract
Motivated by the need to understand the role of internal interfaces in Li migration occurring in lithium-ion batteries, a first-principles study of a coincident site lattice grain boundary in LiFePO4 cathode material and in its delithiated counterpart FPO4 is performed. The structure of the investigated grain boundary is obtained, and the corresponding interface energy is calculated. Other properties, such as ionic charges, magnetic moments, excess free volume, and the lifetime of positrons trapped at the interfaces are determined and discussed. The results show that while the grain boundary in LiFePO4 has desired structural and bonding characteristics, the analogous boundary in FePO4 needs to be yet optimized to allow for an efficient Li diffusion study.
Highlights
A key challenge for developing efficient lithium-ion batteries (LIBs) is to preserve homogeneous Li flows
The coincidence site lattice’ (CSL) is determined by translation vectors a − c, b, and 3c, which implicates that the CSL unit cell volume is three times more than that of the original lattice determined by vectors a, b, and c
configuration 1 (C1) Grain boundaries (GBs) are slightly charged, whereas this effect is negligible for configuration 2 (C2)
Summary
A key challenge for developing efficient lithium-ion batteries (LIBs) is to preserve homogeneous Li flows. Recent investigations [3,4,5,6,7] aimed at studying LFP have combined X-ray spectroscopy and theoretical modeling to monitor the evolution of the redox orbitals in nanoparticles and single-crystal LFP cathodes under different lithiation levels. These studies have provided advanced characterizations techniques for cathodes such as general methods for understanding the relation between lattice distortions and potential shifts [6]. Li diffusion at GBs represents another aspect of the GB effect on the LIB operation [10], since the diffusion along and across the GB may substantially differ
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